Use the balanced combustion reaction above to calculate the enthalpy of combustion for C8H16. C8H16(1)= -174.5kJ/mol. I have no clue how to start this question and need help including the formulas so I know how to do it and some step by step commentary.

Explanation:

C₈H₁₆ + 12O₂ = 8 CO₂ + 8H₂O.

a )

Heat of formation of C₈H₁₆

8 x - 393.5 - 8 x 285.82 + 174.5x 1

= - 5260.06 kJ

b ) Energy required = 2.905 x 10¹⁵kJ

moles of C₈H₁₆ require to be burnt

= 2.905 x 10¹⁵ / 5260.06

= 55.23 x 10¹⁰ moles

= 55.23 x 10¹⁰ x mol weight of C₈H₁₆ g

= 55.23 x 10¹⁰ x 112 g

= 6185.5 x 10¹⁰ g

= 6185.5 x 10⁷ kg

c )

No of litres of CO₂ produced at NTP = 8 x 22.4 x 55.23 x 10¹⁰ L

=  9897.22 x 10¹⁰ L

At 1520 mm of Hg pressure and 250°C

volume of CO₂

= 9897.22  x 10¹⁰ x 760 x ( 273 + 250) / ( 1520 x 273 )

= 9480.3 x 10¹⁰ L .

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol